Multi-material assembly and methods of making thereof

ABSTRACT

A multi-material assembly is provided, as well as methods of making a multi-material assembly. The multi-material assembly includes a first coated structural component and a second structural component. The first coated structural component includes a first uncoated portion, and an adhesive is positioned between the second structural component and the first uncoated portion that secures the first coated structural component to the second structural component.

BACKGROUND

In recent years, high strength steels, particularly manganese-boronsteels have been developed, which achieve high strengths when hot formedwith rapid cooling. Current mass production structural design forvehicles is dominated by such stamped metal, which uses section size,material gauge and grade, and typically spot welding to achieveperformance requirements. To facilitate fuel economy improvement,supported by weight reduction, new concepts are needed to deliverfundamental weight reduction at a reasonable value.

SUMMARY

In accordance with one embodiment, a method of making a multi-materialassembly is provided. The multi-material assembly may be a vehicle framestructural member assembly. The method includes providing an elongatedframe member including a first leg and a second leg. The elongated framemember comprises a coated high strength steel stamping. The coating maycomprise a metal, a metal alloy, or an e-coating. Optionally, thecoating comprises an AlSi alloy. The first leg comprises a firstuncoated portion that is free of the coating. The method furtherincludes providing a reinforcement member including at least a firstfoot. The reinforcement member may comprise a material that isdissimilar from the elongated frame member. The method includes applyingan adhesive to the first foot of the reinforcement member or the firstuncoated portion of the first leg, positioning the reinforcement memberbetween the first leg and the second leg with the first foot positionedopposite the first uncoated portion with the structural adhesivepositioned therebetween, and curing the adhesive to secure the firstfoot to the first uncoated portion.

In accordance with one embodiment, a method of making a multi-materialassembly is provided. The multi-material assembly may be a vehicle framestructural member assembly. The method includes providing a coated highstrength steel blank. The coating may comprise a metal, a metal alloy,or an e-coating. Optionally, the coating comprises an AlSi alloy. Inaddition, the method includes hot-stamping the high strength steel blankto form an elongated frame member including a first leg and a secondleg, treating an interior surface of the first leg of the elongatedframe member to form at least a first uncoated portion that is free ofthe coating, providing a reinforcement member including at least a firstfoot, the reinforcement member may comprise a material that isdissimilar from the elongated frame member, applying an adhesive to thefirst foot of the reinforcement member or the first uncoated portion ofthe first leg, and positioning the reinforcement member between thefirst leg and the second leg with the first foot positioned opposite thefirst uncoated portion with the adhesive positioned therebetween. Inaddition, the method includes positioning an inner frame member oppositethe elongated frame member to define a chamber therebetween. Thereinforcement member is positioned in the chamber with a first matingflange of the inner member positioned opposite a first mating flange ofthe elongated frame member that is positioned on the second end of thefirst leg outward from the first uncoated portion, and a second matingflange of the inner member positioned opposite a second mating flange ofthe elongated frame member. In addition, the method includes welding thefirst mating flange of the inner member to the first mating flange ofthe elongated frame member, welding the second mating flange of theinner member to the second mating flange of the elongated frame memberto form a welded assembly, e-coating the welded assembly, and heatingthe welded assembly to cure the adhesive to secure the first foot to thefirst uncoated portion.

In accordance with one embodiment, a multi-material assembly isprovided. The multi-material assembly may be a vehicle frame structuralmember assembly. The assembly includes an elongated frame memberincluding a first leg and a second leg, the elongated frame membercomprises a coated high strength steel stamping. The coating maycomprise a metal, a metal alloy, or an e-coating. Optionally, thecoating comprises an AlSi alloy. The first leg includes a first portionfree of the coating, and a reinforcement member is provided including atleast a first foot. The reinforcement member may comprise a materialthat is dissimilar from the elongated frame member, and an adhesivepositioned between the first foot and the first uncoated portion thatbonds the reinforcement member to the elongated frame member.

In accordance with one embodiment, a method of making a multi-materialassembly is provided. The multi-material assembly may be a vehicle framestructural member assembly. The method includes providing a firststructural component comprising a coating, wherein the first structuralcomponent comprises a first uncoated portion, providing a secondstructural component optionally comprising a metal or a metal alloy,applying an adhesive to the first uncoated portion or the secondstructural component, positioning the first uncoated portion oppositethe second structural component with the adhesive positionedtherebetween, and curing the adhesive to secure the first structuralcomponent to the second structural component. Optionally, the firststructural component comprises an aluminum alloy casting, the coating isan e-coating, and the second structural component comprises an aluminumalloy or steel, and wherein providing the first structural componentcomprises e-coating the aluminum alloy casting, and treating thee-coated aluminum alloy casting to form the first uncoated portion.Optionally, the first structural component comprises a perimeter, thecoating comprises a metal, a metal alloy, or an e-coating, wherein thefirst uncoated portion is positioned inward of at least a portion of theperimeter, and wherein a second portion of the first structuralcomponent extending from the perimeter to the first uncoated portion iscoated with the coating. Optionally, the first structural componentcomprises an elongated frame member including a first leg and a secondleg, the elongated frame member comprises a high strength steelstamping, wherein the second structural component comprises areinforcement member including at least a first foot having a width thatis less than a width of the first uncoated portion, wherein the step ofapplying the adhesive comprises applying the adhesive to the firstuncoated portion or the first foot, and the step of positioning thefirst uncoated portion opposite the second structural component with theadhesive positioned therebetween comprises positioning the entire widthof the first foot opposite the first uncoated portion with the adhesivepositioned therebetween.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded partial perspective view of a vehicle framestructural member assembly according to an exemplary embodiment of thepresent disclosure shown including an elongated frame member and areinforcement member ready to be assembled onto the elongated framemember.

FIG. 2 is a partial enlarged view taken at the line 2-2 of FIG. 1showing a view of a first foot and a second foot of the reinforcementmember.

FIG. 3 is a cross-sectional view taken along the line 3-3 of FIG. 1 butshown in an assembled state with inner and outer frame members securedto the elongated frame member.

FIG. 4 is a schematic cross-sectional view of the elongated frame memberincluding a first uncoated portion and a second uncoated portionaccording to one aspect of the present disclosure.

FIGS. 5A, 5B, and 5C are a perspective view of an interior surface ofthe elongated frame member including the first uncoated portion and thesecond uncoated portion according to aspects of the present disclosure.

FIG. 6 includes portions of a view of FIG. 3 enlarged for magnificationpurposes.

FIG. 7 includes portions of a view of FIG. 3 enlarged for magnificationpurposes.

FIGS. 8A, 8B, and 8C are schematic cross-sectional views of the secondfoot of the reinforcement member bonded to the second uncoated portionof the elongated frame member with an adhesive according to aspects ofthe present disclosure.

FIG. 9 is a schematic cross-sectional view of the second foot of thereinforcement member bonded to the second uncoated portion of theelongated frame member with an adhesive according to one aspect of thepresent disclosure.

FIG. 10 is a process flow diagram illustrating a vehicle framestructural member assembly method according to an exemplary embodiment.

FIG. 11 is a schematic view of a blank prior to hot-stamping to form theelongated frame member including the first uncoated portion and thesecond uncoated portion according to one aspect of the presentdisclosure.

FIGS. 12A-D are cross-sectional views schematically showing amanufacturing process wherein the reinforcement member iscomplementarily positioned adjacent the elongated frame member andsecured thereto according to one aspect of the present disclosure.

FIG. 13 is an SEM (scanning electron microscope) image showing a crosssection of a comparative test coupon comprising a high strength steelbody coated with AlSi.

FIG. 14 is an SEM image showing a cross section of a test couponcomprising a high strength steel body coated with AlSi and treatedaccording to one aspect of the present disclosure to form an uncoatedportion.

FIG. 15 is an SEM image showing a cross section of a test couponcomprising a high strength steel body coated with AlSi and treatedaccording to one aspect of the present disclosure to form an uncoatedportion.

FIG. 16 is an SEM image showing a cross section of a test couponcomprising a high strength steel body coated with AlSi and treatedaccording to one aspect of the present disclosure to form an uncoatedportion.

DETAILED DESCRIPTION

It should be understood that the description and drawings herein aremerely illustrative and that various modifications and changes can bemade in the compositions, methods and structures disclosed withoutdeparting from the present disclosure.

In general, a multi-material assembly is provided comprising a firstcoated structural component, and a second structural component. Thefirst coated structural component comprises a first uncoated portion,the second structural component is positioned opposite the firstuncoated portion, and an adhesive is provided between the first uncoatedportion and the second structural component to secure the first coatedstructural component to the second structural component. Themulti-material assembly may be a vehicle frame structural memberassembly. In a non-limiting example, the frame structural member and/orthe structural components thereof may be a load-bearing and/or aload-transferring feature or element applied to a vehicle's frame. Thecoating includes, but is not limited to, a metal, a metal oxide, a metalalloy, an e-coating, and any combination thereof.

In an embodiment, a multi-material vehicle frame structural memberassembly is provided comprising a stamped ultra-high strength steelcomponent, such as a boron containing steel, and a method of makingthereof is provided. Before hot stamping, blanks are cut from a roll ofthe ultra-high strength steel. To avoid issues such as surfaceoxidation, the ultra-high strength steel roll or blanks are pre-coatedwith a protective layer. Typically, the coating comprises an aluminumsilicate (AlSi) layer. The blanks may be heated to allow the AlSicoating to bond to the underlying ultra-high strength steel. Withoutbeing limited to any particular theory, more consistent adhesive bondingbetween the stamped ultra-high strength steel component (hereinafterreferred to as “the stamped component”) and a reinforcement is achievedby the removal or absence of the coating between at least a portion ofthe stamped component and the reinforcement.

Referring now to FIGS. 1-16 wherein the showings are for purposes ofillustrating one or more exemplary embodiments and not for purposes oflimiting the same, a vehicle frame structural member assembly 30(hereinafter referred to as “the assembly 30”) according to an exemplaryembodiment is provided. While, for purposes of simplicity ofexplanation, the methods have steps described as executing serially, itis to be understood and appreciated that the present disclosure is notlimited by the illustrated order, and some steps could occur indifferent orders and/or concurrently with other steps from that shownand described herein. As shown in FIGS. 1-3, the assembly 30 includes anelongated frame member 32 (also referred to as a concave framestructure) and a reinforcement member 34 complementarily arrangedadjacent the elongated frame member 32. In an embodiment, the assembly30 includes the elongated frame member 32, the inner frame member 38,and the reinforcement member 34 disclosed in U.S. Patent ApplicationPublication No. US2016/0229457, the contents of which are incorporatedherein by reference. As shown, the elongated frame member 32 of theassembly 30 can be an A-pillar frame member with the reinforcementmember 34 disposed along an upper or windshield portion of the A-pillarframe member (as best shown in FIG. 1). The elongated frame member 32 isformed via hot stamping of a high strength boron-containing steel havingan aluminum silicate (AlSi) coating. An example of such a steel with anAlSi coating is commercially available under the designation Usibor®1500 from ArcelorMittal. An illustrative example of a composition ofUsibor® 1500P is summarized below in weight percentages (the rest isiron (Fe) and unavoidable impurities):

C Mn Si Ni Cr Cu S P Al V Ti B 0.221 1.29 0.28 0.013 0.193 0.01 0.0010.018 0.032 0.005 0.039 0.0038

The reinforcement member 34, which can also be referred to as aninternal reinforcement, has an elongate body 34 a that can be formedfrom a material that is dissimilar from the elongated frame member 32.In a non-limiting example, the reinforcement member 34 comprises apolymeric material, or a metal or metal alloy. In one embodiment, thereinforcement member 34 is formed from a fiber reinforced plasticincluding a plastic matrix material that encapsulates a fiber material.Polymeric materials include, but are not limited to, nylon, polyamide,polyester, polypropylene, polyethylene, or others. The polymericmaterial may be filled or unfilled. For example, the polymeric materialmay be filled with glass, carbon, or other reinforcement fibers. Inanother example, the matrix material can be nylon and/or the fibermaterial can be a plurality of glass fibers. As a more specific example,the matrix material can be nylon that is PA66 or better and/or the glassfibers can be provided in different lengths. In another specificexample, the plastic component of the matrix material can be nylon PPA(polyphthalamide), nylon PAST (poly 1,9-nonamethylene terephthalamide),or some other nylon having a relatively high glass transitiontemperature (Tg), such as relative to nylon PA66.

As shown in FIG. 3, the assembly 30 can include a structural foam 36attached to the reinforcement member 34. The structural foam 36 can be aheat activated epoxy foam. The structural foam 36 can be overmolded ontothe reinforcement member 34 to thereby attach the structural foam 36 tothe reinforcement member 34. In one embodiment, the structural foam 36is a heat activated epoxy foam that is initially overmolded onto thereinforcement member 34 and later heat activated to expand and bond thereinforcement member 34 to the inner frame member 38. For example, thestructural foam 36 can be a heat-activated epoxy-based resin havingfoamable characteristics upon activation through the use of heat such asis received in an e-coat or other automotive/vehicle paint ovenoperation. In particular, as the structural foam 36 is heated, itexpands, cross-links, and structurally bonds to adjacent surfaces. Anexample of a preferred formulation is an epoxy-based material that mayinclude polymer modifiers such as an ethylene copolymer or terpolymerthat is commercially available from L&L Products, Inc. of Romeo, Mich.,under the designations that include L-5505, L-5510, L-5520, L-5540,L-5573 or combinations thereof. Such materials may exhibit propertiesincluding relatively high strength and stiffness, promote adhesion,rigidity, and impart other valuable physical and chemicalcharacteristics and properties. In one exemplary embodiment, thestructural foam is the commercially available material sold under thedesignation L-5520 by L&L Products, Inc., or an equivalent material. Inanother exemplary embodiment, the structural foam is the commerciallyavailable material sold under the designation L5505 by L&L Products,Inc., or an equivalent material.

As best shown in FIG. 3, assembly 30 can further include the inner framemember 38 having mating flanges 38 a, 38 b that mate with inner sides40, 42 of mating flanges 32 a, 32 b of the elongated frame member 32 sothat an interior surface 105 of the inner frame member 38 and aninterior surface 110 of the elongated frame member 32 define a chamber115 that houses the reinforcement member 34. The inner frame member 38can be comprised of the same material and formed in the same manner asthe elongated frame member 32. As shown in the illustrated embodiment,the structural foam 36 is interposed between the reinforcement member 34and the inner frame member 38. The assembly 30 can additionally includean outer frame member 44 having mating flanges 44 a, 44 b that mate withouter sides 46, 48 of the mating flanges 32 a, 32 b of the elongatedframe member 32 on an opposite side of the elongated frame member 32relative to the mating flanges 38 a, 38 b of the inner frame member 38.

The reinforcement member 34 may include the body 34 a, a first foot 50and a second foot 58. A planar surface 50 a of the first foot 50 matesagainst a lower section 52 of the elongated frame member 32. The lowersection 52 and an upper section 60 of the elongated frame member 32together extend from a body 61 of the elongated frame member 32 to formthe elongated frame member 32 as a concave frame structure and arealternately referred to as first and second legs of the concaveelongated frame member 32. The second foot 58 includes an upper wall 58b that mates against the upper section 60 of the elongated frame member32 and an angled wall 62 extending downward from the upper wall 58 btoward the first foot 50, and upward to an outer end 58 a of the secondfoot 58. The upper wall 58 b can be referred to as a shelf and is aplanar surface that is positionable parallel to the upper section 60. Asshown, an adhesive 64 can be interposed between the first foot 50 andthe lower section 52 of the elongated frame member 32. Likewise, theadhesive 64 can be interposed between the second foot 58 and the uppersection 60 of the elongated frame member 32.

The adhesive 64 can have one component or two components. Suitabletwo-component adhesives can be room temperature curing or precuringtwo-component epoxy resin adhesives or polyurethane adhesives or(meth)acrylate adhesives. Room temperature precuring two-component epoxyresin adhesives or polyurethane adhesives or (meth)acrylate adhesivescan be epoxy resin adhesives or polyurethane adhesives or (meth)acrylateadhesives which consist of two components, the mixing of which causes areaction between the components, thus achieving at least a certaindegree of crosslinking (“precured” or “precrosslinked”). Such adhesivesare capable, in a further curing step, of reacting further, for exampleat elevated temperature. These adhesives can have so-called precuring orpregelation in the first stage, and a heat-curing reaction stage atelevated temperature. Two-component epoxy resin adhesives can have aresin component comprising a glycidyl ether, a diglycidyl ether ofbisphenol A and/or bisphenol F. In addition, they can have a hardenercomponent comprising polyamines and/or polymercaptans. Suchtwo-component epoxy resin adhesives can cure rapidly at room temperatureafter mixing of the two components, and are known to those skilled inthe art. Two-component polyurethane adhesives can have polyisocyanatesin one component, such as in the form of prepolymers having isocyanategroups, and polyols and/or polyamines in a second component. Suchtwo-component polyurethane adhesives can cure rapidly at roomtemperature after mixing of the two components and are known to thoseskilled in the art. Two-component (meth)acrylate adhesives can haveacrylic acid and/or methacrylic acid and/or esters thereof in onecomponent. The second component can comprise a free-radical former, suchas a peroxide. Such two-component (meth)acrylate adhesives cure rapidlyat room temperature after mixing of the two components and are known tothose skilled in the art.

As is known by those skilled in the art, room temperature curingtwo-component adhesives can also be cured under the influence of heat.This can lead to a more rapid reaction and thus to a shortening of theperiod of time until an adhesive bond produced therewith can be stressedwith forces. Moreover, a heat treatment of such room temperature curingtwo-component adhesives can lead to higher strengths compared to thosewhich do not undergo any such heat treatment.

In a non-limiting example, the adhesive 64 is a structural adhesive.Structural adhesives are adhesives used to bond structural parts of astructure together, such as for the assembly of the parts of a vehiclesuch as a car, a truck, a bus or a train. After curing, structuraladhesives may bear both high static and high dynamic loads. The curedproduct of a structural adhesive has a lap shear strength of more than18 MPa, optionally more than 21 MPa, and optionally more than 25 MPa.

In one exemplary embodiment, the adhesive 64 can also be a heat-curingone-component epoxy resin adhesive. An example heat-curing one-componentepoxy resin adhesive can comprise at least one epoxy resin and at leastone thermally activable catalyst or a hardener B for epoxy resins whichis activated by elevated temperature. Heating of such a one-componentheat-curing one-component epoxy resin adhesive causes crosslinking. Theheating is effected typically at a temperature of more than 70° C.Exemplary adhesives of this type include those commercially available inthe SikaPower® product line from Sika Automotive AG of Switzerland,including adhesives sold by Sika Automotive AG under the designationSikaPower® 961 and SikaPower®968.

As shown in FIG. 4, the elongated frame member 32 comprises a highstrength steel body 125 with an AlSi coating 130 on the interior surface110 and an exterior surface 120 of the elongated frame member 32. Theelongated frame member 32 is provided with a first uncoated portion 135of the high strength steel body 125 and optionally at least a seconduncoated portion 140 of the high strength steel body 125 that is eitheruncoated with the AlSi protective coating 130, or has had the AlSicoating 130 removed. Accordingly, the first uncoated portion 135 and thesecond uncoated portion 140 are recessed from the outer surface of theAlSi coating 130 to expose the high strength steel body 125 for adhesivebonding with the reinforcement member 34. In a non-limiting example, thefirst uncoated portion 135 and optionally the second uncoated portion140 are recessed at least 25 microns from the outer surface of the AlSicoating 130. The surface of each of the first uncoated portion 135 andthe second uncoated portion 140 extending between the raised surface ofthe AlSi coating 130 may be planar. As shown in FIG. 5A, the firstuncoated portion 135 is positioned inwardly along the first leg 52 froman end 145 of the first leg 52 and the mating flange 32 a, with theregion of the high strength steel body 125 extending between the firstuncoated portion 135 and the end 145 of the first leg 52 including theAlSi coating 130. Similarly, the second uncoated portion 140 ispositioned inwardly along the second leg 60 from an end 150 of thesecond leg 60 and the mating flange 32 b, with the region of the highstrength steel body 125 extending between the second uncoated portion140 and the end 150 of the second leg 60 including the AlSi coating 130.Accordingly, the end 145 of the first leg 52 and the end 150 of thesecond leg 60 at least partially define a perimeter of the elongatedframe member 32, and the first uncoated portion 135 and the seconduncoated portion 140 are positioned inward of at least a portion of theperimeter. Although the first uncoated portion 135 and the seconduncoated portion 140 are shown in FIG. 5A as continuous elongated stripsextending along the length of the elongated frame member 32, it is to beunderstood that the first uncoated portion 135 and the second uncoatedportion 140 are not limited to such shapes or configurations. In anillustrative example, the first uncoated portion 135 and the seconduncoated portion 140 may only extend a portion of the length of theelongated frame member 32. In another non-limiting example as shown inFIG. 5B, the first uncoated portion 135 and the second uncoated portion140 may each comprise a plurality of discrete exposed portions orislands of the high strength steel body 125 with the AlSi coating 130extending therebetween. In a non-limiting example as shown in FIG. 5C,the first uncoated portion 135 and the second uncoated portion 140 maybe non-linear strips extending along all of or a portion of the lengthof the elongated frame member 32.

As best shown in FIG. 5A, the first uncoated portion 135 has a width w₁,the second uncoated portion 140 has a width w₂. The mating flange 32 ahas a width w₃ extending from the first uncoated portion 135 to the end145 of the first leg 52, and the mating flange 32 b has a width w₄extending from the second uncoated portion 140 to the end 150 of thesecond leg 60. In a non-limiting example, the width w₁ is less than thewidth w₃, and the width w₂ is less than the width w₄. In an illustrativeexample, the width w₁ is from 22 mm to 26 mm, and the width w₃ is from22 mm to 24 mm. In an illustrative example, the width w₂ is from 15 mmto 17 mm, and the width w₄ is greater than 22 mm.

As shown in FIG. 6, the adhesive 64 is positioned between the first foot50 of the reinforcement member 34 and the first uncoated portion 135 ofthe high strength steel body 125 to bond the reinforcement member 34 tothe elongated frame member 32. The first foot 50 has a width w₇ thatextends along at least a portion of the width w₁ of the first uncoatedportion 135. As shown in FIG. 7, the adhesive 64 is positioned betweenthe second foot 58 of the reinforcement member 34 and the seconduncoated portion 140 of the high strength steel body 125 to bond thereinforcement member 34 to the elongated frame member 32. The secondfoot 58 has a width w₈ that extends along at least a portion of thewidth w₂ of the second uncoated portion 140. It is to be understood thatthe adhesive 64 may be applied to extend along all or part of the lengthof each of the first foot 50 and the second foot 58. For example, thefirst foot 50 may extend along all or part of the length of the firstuncoated portion 135 with the adhesive 64 positioned therebetween, andthe second foot 58 may extend along all or part of the length of thesecond uncoated portion 140 with the adhesive 64 positionedtherebetween.

Although FIGS. 6 and 7 illustrate the adhesive 64 having a widthextending over the entire width w₁ of the first uncoated portion 135 andthe entire width w₂ of the second uncoated portion 140 of the highstrength steel body 125, it is to be understood that the application ofthe adhesive 64 is not limited to such configurations. The adhesive 64may be applied to have a width that spans only part of the width w₂ ofthe second uncoated portion 140 between the AlSi coating 130 positionedalong each side thereof as shown in FIG. 8A, the adhesive 64 may beapplied to have a width that spans across the entire width w₂ of thesecond uncoated portion 140 between the AlSi coating 130 positionedalong each side thereof as shown in FIG. 8B, or the adhesive 64 may beapplied to have a width that spans across the entire width w₂ of thesecond uncoated portion 140 between the AlSi coating 130 positionedalong each side thereof and overlap the edges of the AlSi coating 130positioned along each side thereof as shown in FIG. 8C. In anon-limiting example, at least 95% of the width of the adhesive 64positioned between the second foot 58 and the second uncoated portion140 is positioned within the width w₂ of the second uncoated portion140. In a non-limiting example, the ratio of the combined overlap width(w₅+w₆) of the adhesive 64 to the width w₂ of the second uncoatedportion 140 is less than 1:5, optionally less than 1:10, optionally lessthan 1:20, and optionally less than 1:25.

Although the second foot 58 is shown in FIGS. 8A, 8B, and 8C as having agreater width w₈ than the width w₂ of the second uncoated portion 140,it is to be understood that the width w₈ of the second foot 58 may bethe same as or less than the width w₂ of the second uncoated portion 140as shown in FIG. 9. For example, when the width w₈ of the second foot 58is less than the width w₂ of the second uncoated portion 140, the entirewidth w₈ of the second foot 58 may be positioned along the high strengthsteel body 125 within the width w₂ of the second uncoated portion 140.Therefore, the surface area of the upper wall 58 b available for bondingto the elongated frame member 32 is positioned opposite the seconduncoated portion 140 so that it may be entirely bonded with the adhesive64 directly to the high strength steel body 125 without the AlSi coating130 positioned therebetween.

Although the first foot 50 and the first uncoated portion 135 are notshown in FIGS. 8A, 8B, 8C, and 9, the same configurations may beapplied. It is also to be understood that the first foot 50 and firstuncoated portion 135 may have a different configuration with respect tothe application of the adhesive 64 than the second foot 58 and thesecond uncoated portion 140. In a non-limiting example, the first foot50 and the first uncoated portion 135 may have the adhesive 64 appliedin the manner illustrated in FIG. 8A, and the second foot 58 and thesecond uncoated portion 140 may have the structural adhesive 64 appliedin the manner illustrated in FIG. 8C.

It is to be understood that other methods may be used to secure thefirst foot 50 to the first uncoated portion 135 and the second foot 58to the second uncoated portion 140 in addition to the adhesive 64. In anon-limiting example, mechanical fasteners including self-piercingrivets, nails, and flow drill screws, thermal fastening methodsincluding spot welds, friction stir welds, friction stir spot welds, andcombinations thereof may be used in addition to the adhesive 64.

With reference now to FIGS. 10, 11, and 12A-12D, a vehicle framestructural member assembly method will now be described. In particular,the method can be used with the vehicle frame structural member assembly30 described hereinabove and will be described with reference thereto,though this is not required and other vehicle frame structural memberassemblies can be used. In the method of FIG. 10, at S200, an elongatedframe member 32 is provided that includes the high strength steel body125 with an AlSi coating 130 applied to an interior surface 110 and anexterior surface 120. The interior surface 110 of the elongated framemember 32 includes a first uncoated portion 135 and optionally a seconduncoated portion 140 of the high strength steel body 125. The presentdisclosure is not limited in any way with respect to the formation ofthe first uncoated portion 135 and the second uncoated portion 140.

In a non-limiting example as shown in FIG. 11, a high strength steelblank 155 may be provided with the AlSi coating 130. The AlSi coating130 may be applied to the high strength steel blank 155 in a manner thatdoes not coat the first uncoated portion 135 and the second uncoatedportion 140. Alternatively, the blank 155 may be coated with the AlSicoating 130, and the blank 155 may be treated chemically or mechanicallyto remove portions of the coating 130 to form the first uncoated portion135 and the second uncoated portion 140. Illustrative examples ofmechanical removal include grinding with, for example, wire wheels, andabrasive blasting with any suitable abrasive material such as shotblasting with metal shot, sand blasting, and glass bead blasting. Theblank 155 may then be transferred to a hot stamping operation where theelongated frame member 32, as best shown in FIG. 5A, is formed.Alternatively, the blank 155 may be coated with the AlSi coating 130 andtransferred to a hot stamping operation to form the elongated framemember 32. The elongated frame member 32 may then be treated to removesome of the AlSi coating 130 to form the first uncoated portion 135 andthe second uncoated portion 140.

In a non-limiting example, the thickness of the AlSi coating 130 to beremoved to form the first uncoated portion 135 and the second uncoatedportion 140 is greater than 20 microns. In a non-limiting example, thethickness of the AlSi coating 130 is 30 microns, and 30 microns of theAlSi coating is removed to form the first uncoated portion 135 and thesecond uncoated portion 140. It is to be understood that not all of theAlSi coating 130 might not be removed to form the first uncoated portion135 and the second uncoated portion 140, as some residual AlSi coating130 or other impurities may remain bonded to the underlying highstrength steel body 125. In a non-limiting example, the first leg 52 istreated to remove at least 25 microns of the AlSi coating 130 to formthe first uncoated portion 135.

Next, at S202, the adhesive 64 is applied to one or both of thereinforcement member 34 and the first uncoated portion 135. For example,the adhesive 64 may be applied to the surface 50 a of the first foot 50and the upper wall 58 b of the second foot 58. The adhesive 64 may beapplied to the first uncoated portion 135 and the second uncoatedportion 140 as shown in FIG. 12A, or the structural adhesive may beapplied to each of the surface 50 a, the upper wall 58 b, the firstuncoated portion 135, and the second uncoated portion 140. Followingapplication of the adhesive 64, at S204, the reinforcement member 34 ispositioned adjacent the elongated frame member 32 to position theadhesive 64 between the first uncoated portion 135 and the first foot50, and between the second uncoated portion 140 and the second foot 58.In addition or in the alternative, complementarily positioning thereinforcement member 34 in S204 can include temporarily securing thereinforcement member 34 to the elongated frame member 32 as shown inFIG. 12B. It is to be understood that the adhesive 64 can be applied asone or more beads. As shown in the illustrative example of FIG. 12A,beads 64 can be applied to the first uncoated portion 135 of theelongated frame member 32 and the bead 64 can be applied to the seconduncoated portion 140 of the elongated frame member 32.

Alternatively or in addition, and as shown in FIG. 12B, temporarilysecuring the reinforcement member 34 to the elongated frame member 32 inS204 can include mechanically fastening the reinforcement member 34 tothe elongated frame member 32. For example, this can be achieved byreceipt of the attachment clips 98 in the apertures 100 of the elongatedframe member 32. Notably, the attached structural foam 36 remains in thenon-expanded state, as illustrated in FIGS. 12A and 12B.

The method of FIG. 10 can additionally include installing the outerframe member 44 and installing the inner frame member 38 at S206.Installing the outer frame member 44 can be done by welding the matingflanges 44 a, 44 b of the outer frame member 44 to the outer sides 46,48 of the mating flanges 32 a, 32 b of the elongated frame member 32.Installation of the inner frame member 38 can include welding matingflanges 38 a, 38 b of the inner frame member 38 to inner sides 40, 42 ofthe mating flanges 32 a, 32 b of the elongated frame member 32. FIG. 12Cshows the inner frame member 38 installed and continues to show thestructural foam 36 in the non-expanded state. Once the inner framemember 38 is installed to the elongated frame member 32 to form thechamber 115 with the reinforcement member 34 positioned therein, thestructural foam 36 is disposed between the reinforcement member 34 andthe inner frame member 38.

Next, as shown at S208 in FIG. 10, the assembly 30 can be coated with acorrosion prevention layer. The coating can be an epoxy-based coating.In one example, the coating can be applied to the assembly 30 by anelectrodeposition coating process, also known as e-coating. In suchexample, e-coating can include any of a variety of suitable compositionsand methods for e-coating, any of which can be used to apply thee-coating to the assembly 30. Generally, e-coating can includesubmerging the assembly 30 into an electrodeposition bath in ane-coating tank, which can include, a binder resin, a synthetic resin,and optionally, a pigment and other additives dissolved or dispersed ina solvent. In an example, an epoxy resin can be used, along with any ofa variety of other suitable resins. Upon immersion into the e-coatingtank, the assembly 30 can come into contact with electrodes such that avoltage can be applied between the cathode and an anode to providecurrent through the electrodeposition bath resulting in the applicationof the e-coating on the assembly 30. In one example, the assembly 30 canundergo electrodeposition one or more times, and in some embodiments,the assembly 30 can be washed between coatings, post-coating, or both.After the e-coating is formed, the e-coating can be cured by baking theassembly 30 in an oven. In certain examples, the oven can be heated toabout 150° C. or greater; in other examples, the oven can be heated toabout 180° C. or greater; and in other examples, the oven can be heatedto about 195° C. or greater. It is to be understood that the structuralfoam 36 and the adhesive 64 may be cured before or after application ofthe e-coating. In an illustrative example, the structural foam 36 andthe adhesive 64 are cured in the same oven step as the e-coating.

At Step S210, the structural foam 36 can be heated. As already describedherein, the structural foam 36 can be heat activated epoxy foam thatexpands and bonds to components in which it is in contact. The heatingof the structural foam in step S208 or S210 causes the structural foam36 to fully fill the gap distance between the reinforcement member 34and the inner frame member 38 as shown in FIG. 12D. In addition, ascured, the structural foam 36 bonds to the reinforcement member 34 andthe inner frame member 38 thereby securing the reinforcement member 34and the inner frame member 38 together. Heating of the structural foamin S208 or S210 can additionally include heating of the adhesive 64,which can have the effect of curing the adhesive 64. In one embodiment,the heating in S210 occurs during the paint oven process in which thevehicle or at least the vehicle frame has paint applied thereto that isthen heated in a paint oven as is known and understood by those skilledin the art.

Although described herein with respect to an AlSi coated stampedultra-high strength steel component and a reinforcement, the presentdisclosure is not limited to such. In an illustrative example, the firststructural component is an e-coated aluminum casting, and the secondstructural component is an aluminum alloy or steel member. The firststructural component includes a first uncoated portion. The uncoatedportion may be provided by masking the aluminum casting duringe-coating, or by treating the e-coated aluminum casting to remove aportion of the e-coating therefrom. The second structural component ispositioned opposite the first uncoated portion and an adhesive ispositioned therebetween. The resulting assembly can be e-coated and theadhesive cured to secure the first component to the second component.The multi-material assembly may be a vehicle frame structural memberassembly.

In an illustrative example, one or both of a first structural componentcomprising a coated steel or aluminum alloy and a second structuralmember optionally comprising a steel or aluminum alloy may have athickness that is too great for adequately securing the first structuralcomponent to the second structural component with mechanical or thermalfastening methods. The first structural component includes a firstuncoated portion. The second structural component is positioned oppositethe first uncoated portion and an adhesive is positioned therebetween tosecure the first structural component to the second structuralcomponent. The multi-material assembly may be a vehicle frame structuralmember assembly.

Examples

The exemplifying embodiments that follow are intended to explain thepresent disclosure further, the selection of examples not being intendedto represent any limitation of the scope of the subject matter of thepresent disclosure.

Elongated frame members 32 as shown in FIG. 5A were formed byhot-stamping. The elongated frame members 32 comprised a high strengthsteel commercially available under the designation Usibor® 1500 fromArcelorMittal and included a 30 micron AlSi coating.

Comparative samples 1-3 were prepared from elongated frame members 32that did not undergo any treatment to remove the AlSi coating (see FIG.13). Coupons of the AlSi coated high strength steel were bonded with astructural adhesive to a JAC980YL steel coupon (JAC980YL is ahigh-strength dual phase steel defined according to the Japan Iron andSteel Federation Standard) to form comparative samples 1-3 forcross-tension shear testing.

Inventive samples 1-3 were prepared from elongated frame members 32 thatunderwent treatment in accordance with the present disclosure to removeAlSi coating to form the uncoated portion. In particular, inventivesamples 1-3 were treated by sand blasting for 10 seconds (FIG. 14).Coupons of the AlSi coated high strength steel were bonded with astructural adhesive applied to the uncoated portion to a JAC980YL steelcoupon to form inventive samples 1-3 for cross-tension shear testing.

Inventive samples 4-6 were prepared from elongated frame members thatunderwent treatment in accordance with the present disclosure to removeAlSi coating to form the uncoated portion. In particular, inventivesamples 4-6 were treated by sand blasting for 30 seconds (FIG. 15).Coupons of the AlSi coated high strength steel were bonded with astructural adhesive applied to the uncoated portion to a JAC980YL steelcoupon to form inventive samples 4-6 for cross-tension shear testing.

As shown in FIGS. 14 and 15, treatment of the elongated members 32 forat least 10 seconds was sufficient to remove the AlSi coating.

In addition, elongated frame members 32 were treated in accordance withthe present disclosure to mechanically remove the AlSi coating to formthe uncoated portion with a wire wheel for 30 seconds (FIG. 16). Otherelongated frame members 32 were treated in accordance with the presentdisclosure to mechanically remove the AlSi coating to form the uncoatedportion with a wire wheel for 30 seconds followed by sand blasting for10 seconds. Other elongated frame members 32 were treated in accordancewith the present disclosure to mechanically remove the AlSi coating toform the uncoated portion with a wire wheel for 30 seconds and sandblasting for greater than or equal to one minute. Some of the samplestreated with only the wire wheel for 30 seconds resulted in the removalof the AlSi coating. However, as shown in FIG. 16, some of the samplestreated with only the wire wheel for 30 seconds resulted in partialremoval of the AlSi coating 130. Treatment with the wire wheel and sandblasting resulted in the complete removal of the AlSi coating 130.

The results of some of the cross-tension shear testing are shown inTable 1.

TABLE 1 Standard Cross-Tension Standard Average Deviation Shear TestingDeviation Treatment to Remove Maximum Maximum Average Tensile TensileAl—Si Coating Load (N) Load (N) Stress (MPa) Stress (MPa) ComparativeSamples 1 None 6547 883 434.7 58.2 2 None 3 None Inventive Samples 1 10Second Sand Blast 7624 682 501.3 43.1 2 10 Second Sand Blast 3 10 SecondSand Blast 4 30 Second Sand Blast 7590 142 502.6 6.8 5 30 Second SandBlast 6 30 Second Sand Blast

As shown in Table 1, cross-tension shear testing of comparative samples1-3 (without any treatment to remove any of the coating) resulted in anaverage maximum load of 6547N with a standard deviation of 883N, and anaverage tensile stress of 434.7 MPa with a standard deviation of 58.2MPa. Cross-tension shear testing of inventive samples 1-3 (with a 10second sand blast treatment to remove a portion of the coating) resultedin an average maximum load of 7624N with a standard deviation of 682N,and an average tensile stress of 501.3 MPa with a standard deviation of43.1 MPa. Cross-tension shear testing of inventive samples 4-6 (with a30 second sand blast treatment to remove a portion of the coating)resulted in an average maximum load of 7590N with a standard deviationof 142N, and an average tensile stress of 502.6 MPa with a standarddeviation of 6.8 MPa.

Although removal of the AlSi coating 130 in accordance with the presentdisclosure does not necessarily result in a substantial difference fromthe comparative samples with respect to the maximum load and tensilestress, the inventive samples of the present disclosure do exhibit asubstantial improvement in the standard deviation of the maximum loadand tensile stress. As the standard deviation is narrower, thecomponents of the assembly 30 of the present disclosure can be designedto reduce weight of the assembly 30, as the parts do not have to befabricated from a thicker or heavier grade of material to accommodatethe worst case scenario (lowest maximum load and tensile strength).Performance repeatability is also improved.

Without being limited to any particular theory, sandblasting for morethan 10 seconds further removes from the high strength steel body 125 atleast some impurities or any ternary layer of alloy at the interface ofthe high strength steel body and the AlSi coating 130, further improvingthe consistency of bonding between the adhesive 64 and the high strengthsteel body 125.

It will be appreciated that various of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also thatvarious presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art which are also intended to beencompassed by the following claims.

What is claimed is:
 1. A method of making a multi-material assemblycomprising: providing an elongated frame member including a first legand a second leg, the elongated frame member comprising a high strengthsteel stamping, the steel stamping comprising a metal or a metal alloycoating, wherein the first leg comprises a first uncoated portion;providing a reinforcement member including at least a first foot;applying an adhesive to the first foot of the reinforcement member orthe first uncoated portion of the first leg; positioning thereinforcement member between the first leg and the second leg with thefirst foot positioned opposite the first uncoated portion with theadhesive positioned therebetween; and curing the adhesive to secure thefirst foot to the first uncoated portion.
 2. The method of claim 1,wherein the reinforcement member comprises a material that is dissimilarfrom the elongated frame member, wherein the coating comprises an AlSialloy, wherein the elongated frame member includes a body, the first legincludes a first end connected to the body and a second end extendingoutward from the body, wherein the first uncoated portion is positionedbetween the first end and the second end of the first leg, wherein thefirst leg extending from the first end to the first uncoated portion iscoated with the AlSi alloy, and the first leg extending from the firstuncoated portion to the second end is coated with the AlSi alloy.
 3. Themethod of claim 2, further comprising: treating the second leg to form asecond uncoated portion; and applying an adhesive to a second foot ofthe reinforcement member or the second uncoated portion, whereinpositioning the reinforcement member between the first leg and thesecond leg includes positioning the second foot opposite the seconduncoated portion with the adhesive positioned therebetween, and whereinthe step of curing the adhesive secures the second foot to the seconduncoated portion.
 4. The method of claim 2, wherein the first leg istreated to remove at least 25 microns of the AlSi alloy coating to formthe first uncoated portion.
 5. The method of claim 4, wherein the firstuncoated portion is recessed from the AlSi alloy coating.
 6. The methodof claim 2, wherein the first foot comprises a width that is less than awidth of the first uncoated portion, and wherein the entire width of thefirst foot is positioned opposite the first uncoated portion.
 7. Themethod of claim 2, wherein the cured adhesive positioned between thefirst foot and the first uncoated portion is positioned entirely withinthe width of the first uncoated portion.
 8. The method of claim 2,wherein at least 95% of the width of the adhesive positioned between thefirst foot and the first uncoated portion is positioned within the widthof the first uncoated portion.
 9. The method of claim 2, furthercomprising: providing an inner frame member including a first matingflange and a second mating flange; and positioning the inner framemember opposite the elongated frame member to define a chambertherebetween, wherein the reinforcement member is positioned in thechamber, wherein the first mating flange of the inner member ispositioned opposite a first mating flange of the elongated frame memberthat is positioned on the second end of the first leg outward from thefirst uncoated portion, and the second mating flange of the inner memberis positioned opposite a second mating flange of the elongated framemember, wherein the step of positioning the inner frame member oppositethe elongated frame member occurs after positioning the reinforcementmember between the first leg and the second leg of the elongated memberand before curing the adhesive.
 10. The method of claim 1, wherein thestep of providing an elongated frame member comprises providing a highstrength steel blank coated with an AlSi alloy coating, hot-stamping thehigh strength steel blank to form the elongated frame member, treatingan interior surface of the first leg to form the first uncoated portion,and wherein the method further comprises: positioning an inner framemember opposite the elongated frame member to define a chambertherebetween, wherein the reinforcement member is positioned in thechamber, wherein a first mating flange of the inner frame member ispositioned opposite a first mating flange of the elongated frame memberthat is positioned on the second end of the first leg outward from thefirst uncoated portion, and a second mating flange of the inner memberis positioned opposite a second mating flange of the elongated framemember; welding the first mating flange of the inner member to the firstmating flange of the elongated frame member, and welding the secondmating flange of the inner member to the second mating flange of theelongated frame member to form a welded assembly; e-coating the weldedassembly; and heating the welded assembly to cure the adhesive to securethe first foot to the first uncoated portion.
 11. A multi-materialassembly comprising: an elongated frame member including a first leg anda second leg, the elongated frame member comprising a coated highstrength steel stamping, wherein the first leg includes a first uncoatedportion; a reinforcement member including at least a first foot; and anadhesive positioned between the first foot and the first uncoatedportion that secures the reinforcement member to the elongated framemember.
 12. The assembly of claim 11, wherein the reinforcement membercomprises a material that is dissimilar from the elongated frame member,wherein the coating comprises an AlSi alloy, wherein the elongated framemember includes a body, the first leg includes a first end connected tothe body and a second end extending outward from the body, wherein thefirst uncoated portion is positioned between the first end and thesecond end of the first leg, wherein the first leg extending from thefirst end to the first uncoated portion is coated with the AlSi alloy,and the first leg extending from the first uncoated portion to thesecond end is coated with the AlSi alloy.
 13. The assembly of claim 12,wherein the reinforcement includes a second foot, the second legincludes a second uncoated portion, the second leg includes a first endconnected to the body of the elongated frame member and a second endextending outward from the body, the second uncoated portion ispositioned between the first end and the second end of the second leg,the second leg extending from the first end of the second leg to thesecond uncoated portion is coated with the AlSi alloy, and the secondleg extending from the second uncoated portion to the second end of thesecond leg is coated with the AlSi alloy, and wherein an adhesive ispositioned between the second foot of the reinforcement member and thesecond uncoated portion to secure the second foot to the second leg. 14.The assembly of claim 13, wherein the first uncoated portion is recessedat least 25 microns from the AlSi alloy coating.
 15. The assembly ofclaim 13, wherein the first foot comprises a width that is less than awidth of the first uncoated portion.
 16. The assembly of claim 13,wherein at least 95% of the width of the adhesive positioned between thefirst foot and the first uncoated portion is positioned within the widthof the first uncoated portion.
 17. A method of making a multi-materialassembly comprising: providing a first structural component comprising acoating, wherein the first structural component comprises a firstuncoated portion; providing a second structural component; applying anadhesive to the first uncoated portion or the second structuralcomponent; positioning the first uncoated portion opposite the secondstructural component with the adhesive positioned therebetween; andcuring the adhesive to secure the first structural component to thesecond structural component.
 18. The method of claim 17, wherein thefirst structural component comprises an aluminum alloy casting, thecoating is an e-coating, and the second structural component comprisesan aluminum alloy or steel, and wherein providing the first structuralcomponent comprises e-coating the aluminum alloy casting, and treatingthe e-coated aluminum alloy casting to form the first uncoated portion.19. The method of claim 17, wherein the first structural componentcomprises a perimeter, the coating comprises a metal, a metal alloy, oran e-coating, wherein the first uncoated portion is positioned inward ofat least a portion of the perimeter, wherein a second portion of thefirst structural component extending from the perimeter to the firstuncoated portion is coated with the coating.
 20. The method of claim 19,wherein the first structural component comprises an elongated framemember including a first leg and a second leg, the elongated framemember comprises a high strength steel stamping, wherein the secondstructural component comprises a reinforcement member including at leasta first foot having a width that is less than a width of the firstuncoated portion, wherein the step of applying the adhesive comprisesapplying the adhesive to the first uncoated portion or the first foot,and the step of positioning the first uncoated portion opposite thesecond structural component with the adhesive positioned therebetweencomprises positioning the entire width of the first foot opposite thefirst uncoated portion with the adhesive positioned therebetween.